Water-in-oil emulsion slurry blasting compositions are well-known in the art. See, for example, U.S. Pat. Nos. 3,161,551; 4,141,767; 4,216,040; 4,231,821; and 4,322,258. These compositions contain a continuous organic liquid fuel phase throughout which is dispersed droplets of an aqueous or aqueous-miscible inorganic oxidizer salt solution phase. With respect to the term "water-in-oil," any highly polar, hydrophilic liquid or melt falls into the "water" category and hydrophobic, nonpolar liquids are considered "oils." In contrast to slurry blasting compositions containing a continuous aqueous phase, which generally are thickened and cross-linked for desired viscosity and water-resistance, emulsion slurry blasting compositions do not require thickeners and cross-linkers for water resistance, since the external phase is water-immiscible and the viscosity of the emulsion slurry blasting composition can be varied by the degree of refinement of the dispersed or emulsified droplets of water-miscible phase or internal phase. Emulsion slurry blasting compositions have other advantageous properties as described in the above-referenced patents.
Emulsion slurries normally are fluid when initially formulated and thus are pumped from a mixing chamber into packages or boreholes. A major problem with handling emulsion slurries is the difficulty in pumping them at the relatively high viscosities required in certain applications. For example, emulsion slurries need to be viscous enough to resist running into cracks and fissures in boreholes, to resist erosional effects of dynamic water, or to resist gravitational flow when loaded into upwardly extending boreholes. Past efforts at handling relatively viscous emulsion slurries either required expensive, heavy duty pumps capable of producing high pressure heads, which pumps also may exert destructive forces on the stability of the emulsion or on its ingredients (such as hollow, spherical density reducing agents), or some type of lubricating system in the hose or delivery conduit, such as injecting an annular stream of liquid around the pumped emulsion slurry to lubricate its flow through the hose.
The present invention provides a method whereby emulsion slurries readily can be pumped through loading or delivery conduits or hoses at relatively low viscosities, but exit from the hose at the desired higher viscosities. This is accomplished by pumping the emulsion slurry through a valve positioned at or near the end of the delivery hose to impart shear to the composition and thereby increase its viscosity prior to its expulsion from the hose. In this fashion, thin, easily pumped emulsion slurry can be delivered through a hose at a relatively low pumping pressure. Upon exit from the hose, the emulsion slurry has a desired higher viscosity. Thus the use of high pumping pressures or additional lubricating systems can be avoided.